Base stations of a cellular radio network broadcast information about themselves and their environment continuously. Such network configuration information may contain, for instance a location area identifier, a base station identifier, a base station type identifier and so-called neighboring cell information. When being currently registered to a base station of a particular cell, a mobile station also monitors the quality of the transmission of the base stations indicated by the neighboring cell information of the current base station and moves to some of these base stations if the field strength of the present base station becomes lower. The cellular network knows the location of the mobile station usually with an accuracy of a so-called location area, to which belong a suitable number of predetermined cells with their base stations. The location area information sent by the base station indicates to the mobile station to which location area the base station belongs. When the mobile station moves to another cell within the same location area, no location updating is needed in the cellular network. On the other hand, upon observing on the basis of location area information a change of location area when moving to a coverage area of a new base station, the mobile station initiates a location updating by sending a location updating request to the cellular network. As a consequence of this location updating request, the cellular network stores the new location area of the mobile station in subscriber registers.
In the future, it is conceivable that both public cellular networks maintained by different operators and several kinds of private Customer Premises Networks (CPN) will be utilized, such as, for instance Business Customer Premises Networks (BCPN), Domestic Customer Premises Networks (DCPN), and Mobile Customer Premises Networks (MCPN). In such a situation, it would be preferable for the service of the networks that a mobile station would be capable of registering automatically or manually to these different networks. The public cellular networks and the CPNs would have separate location area structures. The amount of location updates would be high in such an environment, with the user moving from one place to another. In particular areas of the network, for instance at the edges of a private cellular network, signals of the other networks are so strong that a mobile station may try to initiate the location updates to an external network. Such location updates are unnecessary and annoying when the user wishes to remain registered within the area of a particular network, irrespective of received signal level, for instance. Moreover, unnecessary location updates and location updating attempts cause an unreasonable increase of the signaling load of the network.